// ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
/*==============================================================================
** 
** Class: Stack 
**
** Purpose: An array implementation of a stack. 
**
**
=============================================================================*/
namespace System.Collections { 
    using System;
    using System.Security.Permissions; 
    using System.Diagnostics; 


    public class Stack : ICollection{
        private Object[] _array;     // Storage for stack elements 
        private int _size;           // Number of items in the stack. 
        private int _version;        // Used to keep enumerator in sync w/ collection.
    
        private Object _syncRoot;

        private const int _defaultCapacity = 10;
 
        public Stack() {
            _array = new Object[_defaultCapacity]; 
            _size = 0; 
            _version = 0;
        } 

        // Create a stack with a specific initial capacity.  The initial capacity
        // must be a non-negative number.
        public Stack(int initialCapacity) { 
            if (initialCapacity < 0)
                throw new ArgumentOutOfRangeException("initialCapacity", ("ArgumentOutOfRange_NeedNonNegNum")); 
            if (initialCapacity < _defaultCapacity) 
                initialCapacity = _defaultCapacity;  // Simplify doubling logic in Push.
            _array = new Object[initialCapacity]; 
            _size = 0;
            _version = 0;
        }
 
        // Fills a Stack with the contents of a particular collection.  The items are
        // pushed onto the stack in the same order they are read by the enumerator. 
        // 
        public Stack(ICollection col) : this((col==null ? 32 : col.Count))
        { 
            if (col==null)
                throw new ArgumentNullException("col");
            IEnumerator en = col.GetEnumerator();
            while(en.MoveNext()) 
                Push(en.Current);
        } 
 
        public virtual int Count {
            get { return _size; } 
        }

        public virtual bool IsSynchronized {
            get { return false; } 
        }
 
        public virtual Object SyncRoot { 
            get {
                if( _syncRoot == null) { 
                    System.Threading.Interlocked.CompareExchange(ref _syncRoot, new Object(), null);
                }
                return _syncRoot;
            } 
        }
 
        // Removes all Objects from the Stack. 
        public virtual void Clear() {
            Array.Clear(_array, 0, _size); // Don't need to doc this but we clear the elements so that the gc can reclaim the references. 
            _size = 0;
            _version++;
        }
 
        public virtual Object Clone() {
            Stack s = new Stack(_size); 
            s._size = _size; 
            Array.Copy(_array, 0, s._array, 0, _size);
            s._version = _version; 
            return s;
        }

        public virtual bool Contains(Object obj) { 
            int count = _size;
 
            while (count-- > 0) { 
                if (obj == null) {
                    if (_array[count] == null) 
                        return true;
                }
                else if (_array[count] != null && _array[count].Equals(obj)) {
                    return true; 
                }
            } 
            return false; 
        }
 
        // Copies the stack into an array.
        public virtual void CopyTo(Array array, int index) {
            if (array==null)
                throw new ArgumentNullException("array"); 
            if (array.Rank != 1)
                throw new ArgumentException(("Arg_RankMultiDimNotSupported")); 
            if (index < 0) 
                throw new ArgumentOutOfRangeException("index", ("ArgumentOutOfRange_NeedNonNegNum"));
            if (array.Length - index < _size) 
                throw new ArgumentException(("Argument_InvalidOffLen"));

            int i = 0;
            if (array is Object[]) { 
                Object[] objArray = (Object[]) array;
                while(i < _size) { 
                    objArray[i+index] = _array[_size-i-1]; 
                    i++;
                } 
            }
            else {
                while(i < _size) {
                    array.SetValue(_array[_size-i-1], i+index); 
                    i++;
                } 
            } 
        }
 
        // Returns an IEnumerator for this Stack.
        public virtual IEnumerator GetEnumerator() {
            return new StackEnumerator(this);
        } 

        // Returns the top object on the stack without removing it.  If the stack 
        // is empty, Peek throws an InvalidOperationException. 
        public virtual Object Peek() {
            if (_size==0) 
                throw new InvalidOperationException(("InvalidOperation_EmptyStack"));
            return _array[_size-1];
        }
 
        // Pops an item from the top of the stack.  If the stack is empty, Pop
        // throws an InvalidOperationException. 
        public virtual Object Pop() { 
            if (_size == 0)
                throw new InvalidOperationException(("InvalidOperation_EmptyStack")); 
            _version++;
            Object obj = _array[--_size];
            _array[_size] = null;     // Free memory quicker.
            return obj; 
        }
 
        // Pushes an item to the top of the stack. 
        //
        public virtual void Push(Object obj) { 
            if (_size == _array.Length) {
                Object[] newArray = new Object[2*_array.Length];
                Array.Copy(_array, 0, newArray, 0, _size);
                _array = newArray; 
            }
            _array[_size++] = obj; 
            _version++; 
        }
 

 

        // Copies the Stack to an array, in the same order Pop would return the items.
        public virtual Object[] ToArray()
        { 
            Object[] objArray = new Object[_size];
            int i = 0; 
            while(i < _size) { 
                objArray[i] = _array[_size-i-1];
                i++; 
            }
            return objArray;
        }
 
     
 

       private class StackEnumerator : IEnumerator
        {
            private Stack _stack;
            private int _index;
            private int _version; 
            private Object currentElement;
 
            internal StackEnumerator(Stack stack) { 
                _stack = stack;
                _version = _stack._version; 
                _index = -2;
                currentElement = null;
            }
 
            public Object Clone()
            { 
                return MemberwiseClone(); 
            }
 
            public virtual bool MoveNext() {
                bool retval;
                if (_version != _stack._version) throw new InvalidOperationException(("InvalidOperation_EnumFailedVersion"));
                if (_index == -2) {  // First call to enumerator. 
                    _index = _stack._size-1;
                    retval = ( _index >= 0); 
                    if (retval) 
                        currentElement = _stack._array[_index];
                    return retval; 
                }
                if (_index == -1) {  // End of enumeration.
                    return false;
                } 

                retval = (--_index >= 0); 
                if (retval) 
                    currentElement = _stack._array[_index];
                else 
                    currentElement = null;
                return retval;
            }
 
            public virtual Object Current {
                get { 
                    if (_index == -2) throw new InvalidOperationException(("InvalidOperation_EnumNotStarted")); 
                    if (_index == -1) throw new InvalidOperationException(("InvalidOperation_EnumEnded"));
                    return currentElement; 
                }
            }

            public virtual void Reset() { 
                if (_version != _stack._version) throw new InvalidOperationException(("InvalidOperation_EnumFailedVersion"));
                _index = -2; 
                currentElement = null; 
            }
        } 

        internal class StackDebugView {
            private Stack stack;
 
            public StackDebugView( Stack stack) {
                if( stack == null) 
                    throw new ArgumentNullException("stack"); 

                this.stack = stack; 
            }

            [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
            public Object[] Items   { 
                get {
                    return stack.ToArray(); 
                } 
            }
        } 
    }
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
